What Is the Zero-Carb Diet, and Is It Healthy?

Here's what a registered dietician wants you to know.

Diets designed for eating patterns low in carbs have been popular for years. However, a zero-carb diet focuses on not eating any carbs or a very, very small amount of them.

A no-carb diet may be even more restrictive than a keto diet, where a person cannot eat more than a certain amount of carbs. Eating restrictively on a zero-carb diet could lead to health issues and even weight gain. Here's why.

Low-Carb Diets Are Not Always Healthy

One report indicated that the percentage of adults in the U.S. ages 20 and over on a diet on any given day increased to 17.1 %, as did the percentage of people following a low-carb diet (2%).

While there's no precise limit to the grams allowed per day on the zero-carb diet, this approach involves eliminating as much carbohydrate as possible.

Since vegetables typically contain 3-4 grams of net carb (that's grams of total carb minus grams of fiber) per cup, and an ounce of nuts provides about the same, a truly zero-carb goal eliminates more health-protective foods than any other diet.

Cutting Carbs Entirely Is Too Restrictive

When dietary fat was vilified, I saw clients obsessed with avoiding fat at all costs. If something had half a gram of fat per serving, they would banish the food, fearing that those half grams would add up to too many total grams by the end of the day.

This mentality led to filling the fat void with carbs and sugar, leading to weight gain and a host of fat-deficiency side effects, from dry skin to hormone imbalances.

As with fat, the focus on carbohydrates should be quality and balance. Some carbs offer little nutritional value but can be enjoyed in moderation, such as processed grains and refined sugar. Still, other carbs provide health benefits like whole grains, potatoes, legumes—beans, peas, or lentils—and whole fruits.

Here's an analogy: Some types of workouts can lead to injury. But that being true, it doesn't mean you should avoid working out altogether. The goal of exercising is to engage in the right type and amount. The same is true for carbs.

Losing and maintaining a healthy weight and preventing diseases like diabetes doesn't require such extreme carb limits. The side effects of total carb elimination can negatively impact your health and quality of life.

Here are four thoughts to consider.

You Could Miss Out on Important Nutrients

In Blue Zones—areas where people live the longest, healthiest lives—diets are predominantly plant-based and relatively high in carbs. Plant-based diets have been shown to:

  • Support healthy weight
  • Improve insulin resistance
  • Support a healthy gut microbiome
  • Reduce the formation of advanced glycation end products, or AGEs—compounds associated with aging

However, decreasing carbs severely reduces the intake of many critical nutrients in eliminated foods. Those nutrients include vitamins, minerals, antioxidants, fiber, prebiotics, and healthy fats.

No multivitamin or supplements can replace the many health-protective nutrients that stop showing up for work in the body. This shortfall could increase the risk of side effects—like cognitive changes, stroke, or abdominal pain—especially if multiple supplements are used simultaneously at high doses.

It Could Mess With Your Digestion

You get dietary fiber through the foods you eat. Two fiber types—soluble and insoluble— play essential roles in digestion and weight regulation. Because fiber makes you feel fuller, getting enough can help you eat less.

A high-fiber diet is also linked to a significantly lower risk of heart disease, stroke, high blood pressure, and type 2 diabetes. Certain fiber also acts as a prebiotic, or food for the 'good' gut bacteria that support immunity and reduce inflammation. Gut bacteria also may play a significant role in mental health.

Fiber is found only in foods that contain carbohydrates, such as fruits, vegetables, beans, and legumes. The daily recommended target for fiber is at least 25 grams per day for adults.

Fiber supplements are available, but research shows they don't offer the same benefits as fiber derived from whole foods.

You Could Experience 'Low-Carb Flu'

You've probably heard about the keto flu. When people first adopt a keto diet, they can develop symptoms that include headaches, brain fog, irritability, dizziness, nausea, and muscle soreness.

Keto flu happens because your brain, which uses glucose, must adapt to a different fuel source. Your body makes glucose by breaking down carbohydrates. It produces ketones when it breaks down fat. The brain must use ketones on a low-carb diet, leading to uncomfortable side effects.

The symptoms eventually disappear, but just because your body can adapt doesn't mean it's ideal. The same is true of renouncing carbs. Again, it's unnecessary for weight loss or optimal health, so why put yourself through it?

There May Be Mental and Social Side Effects

Any extreme diet makes social eating a challenge. It can also affect your mental health.

I've heard many stories from clients about how their strict diet led to avoiding get-togethers with friends and family or caused them to become obsessive or fearful about food. Others could not keep up with the restrictions and thus "fell off the wagon," then experienced extreme guilt and depression.

Going on and off strict diets is a pattern that can morph into disordered eating, which crushes people's quality of life and mental health.

By contrast, a review of 11 studies concluded that plant-based diets that include healthful carbs are associated with significant improvements in mental health, emotional well-being, and symptoms of depression.

How To Include Carbs in Your Diet

Wiping out an entire macro—meaning no carbs at all, only fat and protein—may be an easier way to lose weight because it's simple, but it's not better. For most, it's not sustainable. Instead:

  • Eat more non-starchy veggies, making them the core of your eating pattern.
  • Include more fruit, whole grains, and starchy veggies in a quantity that aligns with your body's fuel needs.
  • Include healthy, hunger-satisfying fats that are good for circulation, like avocado and avocado oil; extra virgin olive oil and olives; nuts; seeds; and nut/seed butters.
  • Eat more meatless meals that include lentils, beans, and chickpeas as the protein source.

Eating like this is healthier, promotes weight loss, and is more sustainable.

A Quick Review

The bottom line is that a zero-carb diet is not necessary or recommended for either long-term weight loss or optimal health. It can lead to nutrient deficiencies and affect your digestion, immunity, and physical and emotional health if taken to an extreme.

One of the better options includes plant-based diets that include whole, fiber-rich foods; monounsaturated fats, like avocado, olive oil, and nuts; and plant-based proteins, like lentils and beans. This diet may also play a significant role in preventing and managing Type 2 diabetes.

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